Electron tube



y 1944 R. SCHARFNAGEL ELECTRON TUBE "Filed Fb. 4, 1941 j I w 28 B awuvwbd fade/ 5654/31? aye Patented'May 16, 1944 orrlc 2.24am ELECTRON TUBE Rudolf Scharfnagel, Stuttgart, Germany; vested in the Alien Property Custodian Application February 4, 1941, Serial No.

In Germany January 27, 1940 2 Claims. (Cl. 250-275) Electron tubes when employed for high power entail the diflicuity that a great quantity of heat must be conducted away from the electrodes. In the ease of tubes'havlng a metal bulb this bulb usually serves as anode and thus insures a comparatively good heat radiation.

Tubes of this kind are desired to be as small 'as possible and yet to be suitable for high power. The high temperature acquired by the bulb or anode may happen to exceed the softening temperature of the glass seal by which the cover for the bulb and the current leads mounted in the cover are secured to the bulb, and in such case can endanger the seal.

According to the invention a cooling device made of a light metal is inserted over the bulb and positioned near the seal, as will be understoo from the following description and the accompanying drawing, in which Fig. 1 is a, sectional view of an example oi electron tubes as provided by the invention, Fig. 2 is an end view of the cooling device.

The tubular I The cooling device 2 is shown to cover part of the bulb but may be arranged to cover the entire surface thereof. The cooling device acts to protect the seal 3 from softening on the bulb becoming hot. The load capacity of the electron tube hence is greater than heretofore.

The cooling device 2 can be shrunk onto the metal bulb or may be fixed to'it in any other suitable manner, ahd it is made of a light metal or the kind having a very good heat conductivity and a high heat radiation. The cooling device hence. maybe comparatively small and may be accommodated in shape to the bulb, or may be .given any other desirable form. Since durthen more the cooling-device may be located near the seal 3. electron tubes 01 the novel-construction may be very small. Also. twoor more sealing operations may-be effected one alter another and in the neighbourhood of each other without interfering with one another.

It has been found that the cooling action is particularly good it the cooling device 2 is a tu- I metal bulb is designated i. z

denotes the cooling device, 3 theseal.

bular body or ring A formed with cooling fins or vanes B which are longer than this ring, so that each vane B in part freely extends along the bulb, as willbe seen in Fig. 1. Preferably, the bulb is somewhat conical at the zone where ring A is shrunk onto it. Ring A may be short as shown because the cooling device is made of a material to which a good heat conductivity is pedollar and which therefore requires only a compar'atively small part of the device 2 to contact with the bulb.

. This material may be a magnesium alloy designated as E1e'ktron" and which has proved to be most suitable for this purpose, as it is easy to tool and mouldable by die casting thus saving material. 7

What is claimed is:

1. An electron tube comprising, an elongated metallic envelope, a fu'sable seal closing one end of said envelope, and cooling means to maintain the temperature of the fusable seal below a predetermined critical temperature, said cooling means comprising a metallic ring tightly fitted about said envelope adjacent the end thereof which is closed by said seal and a plurality of radially positioned elongated fins mounted on the outer periphery of said ring and positioned longitudinally along said envelope whereby a free space is provided adjacent the ring and about the envelope within the group 01' fins.

2. In combination with an electron tube having a Iusable seal which may be injured by being subjected to an excessive temperature, a cooling means for carrying away the heat from an annular zone on the tube adJacent said seal whereby the heat which is produced remote from said seal is dissipated to the surrounding medium. said cooling means comprising, a metallic ring in tight heat conducting relationship to the surface of the tube. and a plurality of spaced fins interal with the ring and positioned radially with respect to the center of the ring. said fins being spaced from the surface of the tube whereby the pass freely-between the 

